1. Field of the Invention
The present invention relates to a technique for detecting a defocus amount from a phase difference of an image passing through a different pupil area.
2. Description of the Related Art
There has conventionally been a technique of detecting a focusing state of an optical system by changing an accumulation area of a photoelectric conversion element group in an AF sensor. For example, a technical concept has been discussed, in which a signal is output as an accumulation area is changed, so that the number of the focusing-state detection areas is secured or increased, and a detection time can be shortened even if the defocus amount is great (see Japanese Patent Application Laid-Open No. 2006-220684).
There arises a need to increase the number of the focusing-state detection areas, in general. When this need is to be met, there arises an issue how the AF sensor is controlled or how the defocus amount is detected with the use of the output from the AF sensor, since the adjacent focusing-state detection areas come close to each other. When at least a part of the focusing-state detection area is shared by two AF frames, there is a technical issue. Namely, a user who selects a desired AF frame by visually confirming the AF frame, needs to be provided with a technique of detecting a focusing state, which reduces a possibility that a subject in an AF frame different from a desired AF frame is brought into focus.